Automatic identification of products has become commonplace. For example, the ubiquitous barcode label, placed on food, clothing, and other objects, is currently the most widespread automatic identification technology that is used to provide merchants, retailers and shippers with information associated with each object or item of merchandise.
Another technology used for automatic identification products is Radio Frequency Identification (RFID). RFID uses labels or “tags” that include electronic components that respond to radio frequency commands and signals to provide identification of each tag wirelessly. Generally, RFID tags and labels comprise an integrated circuit (IC, or chip) attached to an antenna that responds to a reader using radio waves to store and access the ID information in the chip. Specifically, RFID tags and labels have a combination of antennas and analog and/or digital electronics, which often includes communications electronics, data memory, and control logic.
One of the obstacles to more widespread adoption of RFID technology is that the cost of RFID tags are still relatively high as lower cost manufacturing of RFID tags has not been achievable using current production methods. Additionally, as the demand for RFID tags has increased, the pressure has increased for manufacturers to reduce the cost of the tags, as well as to reduce the size of the electronics as much as possible so as to: (1) increase the yield of the number of chips (dies) that may be produced from a semiconductor wafer, (2) reduce the potential for damage, as the final device size is smaller, and (3) increase the amount of flexibility in deployment, as the reduced amount of space needed to provide the same functionality may be used to provide more capability.
However, as the chips become smaller, their interconnection with other device components, e.g., antennas, becomes more difficult. Thus, to interconnect the relatively small contact pads on the chips to the antennas in RFID inlets, intermediate structures variously referred to as “straps,” “interposers,” and “carriers” are sometimes used to facilitate inlay manufacture. Interposers include conductive leads or pads that are electrically coupled to the contact pads of the chips for coupling to the antennas. These leads provide a larger effective electrical contact area between the chips and the antenna than do the contact pads of the chip alone. Otherwise, an antenna and a chip would have to be more precisely aligned with each other for direct placement of the chip on the antenna without the use of such strap. The larger contact area provided by the strap reduces the accuracy required for placement of the chips during manufacture while still providing effective electrical connection between the chip and the antenna. However, the accurate placement and mounting of the dies on straps and interposers still provide serious obstacles for high-speed manufacturing of RFID tags and labels. Two challenging areas currently facing manufacturers include:
1) Die Attachment: Accurately positioning dies (i.e., chips) for attachment to strap leads is difficult to achieve at the speeds needed to achieve high volume manufacturing.
2) Bonding: It is difficult to accurately bond, cure, and electrically connect the chips to strap leads at rates necessary to achieve high volume manufacturing.
Several possible high-speed strap assembly strategies have been proposed. The first approach, which uses “pick-and-place” machines typically used in the manufacturing of circuit boards for picking up electronic components and placing them on circuit boards, is accurate, but requires expensive machines that ultimately do not deliver a sufficient throughput to justify the increased cost. Another approach, referred to as a “self-assembly process,” is a method in which multiple chips are first dispersed in a liquid slurry, shaken and assembled into a substrate containing chip receiving recesses. Some current processes are described in U.S. Pat. No. 6,848,162, entitled “Method and Apparatus for High Volume Assembly of Radio Frequency Identification Tags,” issued to Arneson, et al. on Feb. 1, 2005; U.S. Pat. No. 6,566,744, entitled “Integrated Circuit Packages Assembled Utilizing Fluidic Self-Assembly,” issued to Gengel on May 20, 2003; and, U.S. Pat. No. 6,527,964, entitled “Methods and Apparatuses for Improved Flow in Performing Fluidic Self Assembly,” issued to Smith et al. on Mar. 4, 2003.
Accordingly, there is a long-felt, but as yet unsatisfied need in the RFID device manufacturing field to be able to produce RFID devices in high volume, and to assemble them at much higher speed per unit cost than is possible using current manufacturing processes.